Rocket measurements of the equatorial airglow: MULTIFOT 92 database

The MULTIFOT airglow photometer payload was launched from Alcântara (2.5°S, 44.4°W) on a SONDA III rocket at 23:52 hrs local time on 31 May 1992. A total of ten photometers, six forward-looking and four side-looking, measured the height profiles of the airglow emissions O₂ Herzberg band system, 01557.7 run, NaD 589.3 nm, 01630.0 nm, OH(8,3) band R branch at 724.0 nm, O₂ Atmospheric (0,0) band at 762.0 nm and the sky background at 578 nm and 710 nm. At the time of launch, a ground-based airglow photometer observed the intensity variations of these emissions, together with the rotational temperature of the OH(9,4) band, and a sodium lidar measured atomic sodium concentration from 80 to 110 km.     

Observations of gravity waves from multispectral mesospheric nightglow emissions observed at 23°S

Simultaneous measurements of the 015 57.7 nm, O₂ atmospheric (0,1) band, NaD and OH (9,4) band emissions obtained during the period October November 1989 at Cachoeira Paulista (23°S, 45°W), Brazil, have been analysed to study gravity waves in the mesospheric region at a low-latitude station in the southern hemisphere. It was found that, when these emissions showed large temporal intensity variations, there were also short period quasi-coherent temporal variations superposed on them, suggesting a possible passage of internal gravity waves in the emission layers. Cross-correlation analysis indicates that the time lag between the different emissions is smaller for short period variations compared with the long period variations. The wave parameters, namely a vertical wavelength of 12 km, a horizontal derived wavelength of 200 km with a period of 80 min, estimated from one of the observed short-period coherent oscillations, are typical of the internal gravity waves at the airglow emission height.     

On the role of the 9.6 μm O3 band in the energetics of the mesosphere and lower thermosphere

Radiative cooling and heating in the 9.6 μm O₃ band has been calculated for the 50–105 km region. The NLTE effects due to the excitation of the ozone ν₃ vibrations by atmospheric and solar radiation and by the release of chemical energy into vibrations upon recombination of O + O₂ into O₃ have been taken into account. It is shown that the LTE approximation is good for altitudes below 70 km where fundamental transitions comprise the main contribution to the cooling rate. Above 70 km, the contribution of the hot transitions to radiative cooling may exceed the contribution of the fundamental ones. In the presence of chemical excitation, part of the chemical energy radiates in the hot transitions, resulting in an additional cooling rate of about 0.5 K/day at 90 km. A method of parameterizing radiative heating which is based on the separation of the effects of fundamental and hot transitions in the 9.6 μm O₃ band is proposed.     

Mesospheric temperatures and the OH layer height as derived from ground-based lidar and OH1 spectrometry

Night-time mesospheric temperatures were simultaneously determined from the Doppler broadening of the D₂ resonance line of atmospheric sodium excited by a laser and from the rotational distribution of the P₁(1), P₁(3) and P₁(4) lines of the OH(3,1) band by an i.r. spectrometer. Both instruments were located at the Andøya Rocket Range (69°N, 16°E). The mesospheric temperature gradient permits determination of the altitude of the OH¹ emitting layer from a comparison of the equivalent layer temperatures calculated from the height-resolved Na Doppler temperatures with the observed OH¹ rotational temperatures. The altitude of the OH¹ layer maximum is determined with an accuracy of ±4 km. For 3 nights in January 1986 the OH¹ emission layer is found near an altitude of 86 km.     

Measurements of odd oxygen in the polar region on 10 February 1984 during MAP/WINE

Abundances of atomic oxygen and ozone have been measured by various techniques over northern Scandinavia during the MAP/WINE campaign in the winter 1983–1984. On 10 February at Kiruna, Sweden, rocket experiments used resonance fluorescence and twin path absorption at 130 nm to measure [O]between 70 and 178 km. Rocket-borne measurements of nightglow at 557.7, 761.9 and 551.1 nm and at 1.27 μm have also been obtained and [O]values derived from the atmospheric band intensities. Ozone abundances between 50 and 90 km have been determined from rocket-borne measurements of the ν₃ 9.6 μm nightglow intensity from Andøya, Norway, and Kiruna. These have been compared with [O₃] measured on the same day from the Solar Mesospheric Explorer satellite, using measurements of dayglow at 1.27 μm, and with results from other rocket launchings in MAP/WINE. The results show evidence of low, perhaps exceedingly low, [O] and below normal [O₃] above the mesopause. Below 75 km at night [O₃] exceeded earlier and subsequent observations in the campaign. The measurements were made during a minor stratospheric warming, characterised by an offset polar vortex centred near the measurement zone.     

Sudden sodium layers in polar latitudes

We discuss in this paper sudden sodium layers (SSLs), which we observe with a sodium lidar instrument at Andenes, Norway (69°N). We speak of a SSL if, in a narrow altitude range (typically less than 2km), the Na density increases over the normal Na density by a factor of at least 2 within 5 min. Between December 1985 and November 1987, we have observed 42 such layers in 378 h of lidar measurements. This number increases to 75 if we only require an increase of a factor of 1.5 within 8 min. At our observation site, SSLs have the following properties: (a) they develop between 90 and 110 km altitude, (b) they develop between 20 and 02 LT, (c) their appearance shows a strong, positive correlation with that of ƒ-type E_s layers, and (d) their appearance does not show a strong correlation with either riometer absorption or meteor showers. We discuss a number of potential processes for SSL formation. SSLs above 100km can be formed in ƒ-type E_s layers by the conversion of Na⁺ ions into neutral Na. The development of SSLs below 95 km requires the presence of an additional reservoir of Na, such as Na-bearing molecules, ions, and/or ‘smoke’ particles. We also evaluate the proposal that SSLs are the outcome of single meteoroids entering the upper atmosphere, a proposition for which we find little observational support.     

The 4.8 and 9.6 μm O3 band emissions in the middle atmosphere

For the 40–115 km atmospheric layer, the populations of 19 vibrational states of the O₃ molecule have been calculated for sets of vertical profiles of temperature and concentration of O and O₃. A peculiar feature of the day and night time vertical profiles of the vibrational temperature of the states is at its maximum in the height range 75–90 km which is due to the formation of vibrationally excited molecules of O₃ in the recombination: O₂ + O + M → O₃ + M. On the basis of the calculated populations of the states, the limb and downward atmospheric emissions in the 4.8 and 9.6 μm O₃ bands have been estimated, as well as the contributions of the constituents of the band of vibrational transitions.     

Sodium density and atmospheric temperature in the mesopause region in polar summer

Sodium lidar measurements have been performed during three summer seasons at a polar latitude (69°N), yielding profiles of sodium number density and temperature of the 85–100 km altitude region. Density measurements were performed during the months of June–August; temperature measurements only were made in August. The sodium layer was found to be both significantly weaker and more variable in summer than in winter. Measurements in summer 1987 yielded an average maximum Na density of about 900 atoms per cm³. The average maximum Na density during summer 1986 and 1988 was near 2600 atoms per cm³. The observed Na column density in summer varied from 3.10⁸ to 3.10⁹ atoms per cm². Temperature measurements were performed in August of 1986 and 1987. Mesopause temperatures of less than 125 K were observed in early August, rising rapidly throughout the month. The mean altitude of the mesopause was found to be about 87 km.     

Net radiative heating in the middle atmosphere

The meridional distributions of both total solar and net radiative heating rates have been obtained between 30 and 110 km at both the solstice and equinox using Fomichev et al.'s total radiative long wave cooling data in the calculations of the net radiative heating. The contributions to the solar heating of O₃, O₂, CO₂ and H₂O have been investigated. For the ozone heating, the absorption of diffusive solar radiation from the ground and troposphere has been estimated. The 50–90 km layer is close to radiative equilibrium on a globally averaged basis. The importance of radiative cooling as an energy sink in the 90–110 km layer is apparently not less than that of the vertical eddy heat conduction. The ordered meridional circulation has been obtained under the assumption that the temperature variation, due to net radiative heating, is balanced by the adiabatic and temperature variations due to vertical air motion. The circulation model obtained is compared with other empirical models, which are reviewed. For the hemisphere and the 60–80 km layer, the two-cell circulation with the rising motion near the equator and pole from spring to autumn and above 80 km, the one-cell circulation with the sinking motion near the equator and equinox, seem to be most realistic. Also quite realistic for the period near the solstice is the same type of two-cell circulation in the 40–50 km layer and the sinking motion at low latitudes in the 50–60 km layer.     

Gravity wave activity in the upper mesosphere over Urbana,Illinois: lidar observations and analysis of gravity wave propagation models

We analyze 375 h of Na Wind/Temperature lidar measurements of the mesopause region (≈ 80–105 km) Na density and temperature profiles on 57 nights distributed over 2 yr at Urbana, Illinois. These observations yield a high-resolution seasonal data set of gravity wave activity in the upper mesosphere. From this data, we present measurements of the Brunt-Väisälä period, the relative atmospheric density perturbations and their spectra, and the parameters of 143 quasi-monochromatic gravity waves. The direct measurement of the Brunt-Väisälä period allows accurate calculation of the horizontal velocity perturbations and vertical displacement perturbations from the density measurements. The horizontal velocity and vertical displacement vertical wave number spectrum magnitudes and indices show considerable seasonal and nightly variability. The gravity wave amplitudes, wavelengths, and observed periods exhibit systematic relationships similar to those found in previous studies, and are consistent with the MU radar measurements of intrinsic gravity wave parameters. Here, we present a detailed analysis of the observations in terms of Diffusive-Filtering Theory models of gravity wave propagation. The magnitudes of the vertical wave number spectrum, the form of the joint vertical wave number and frequency spectrum, and the systematic relationships between the monochromatic gravity wave parameters are consistent with the Diffusive-Filtering model. We compare these results with a variety of radar, lidar, and airglow observations from other sites. This observational study suggests that the complex nonlinear interactions of the gravity wave field may be modeled successfully as a diffusive damping process, where the effective diffusivity is a function of the total wave variance.     

Gravity waves from O2 nightglow during the AIDA '89 campaign III: effects of gravity wave saturation

The O₂ atmospheric (0–1) night airglow emitted within the gravity wave saturation region at ∼90–100 km can serve as a means of studying the wave activity. In this analysis, the atmospheric motions were described by a mean spectral model and an algorithm was developed to infer the wave kinetic energy density and momentum flux from variations in O₂ (0–1) airglow emission rate and rotational temperature. The method was applied to eight nights of data collected by MORTI, a mesopause oxygen rotational temperature imager, during the AIDA campaign of 1989 in Puerto Rico (18°N, 67°W). The observed r.m.s. fractional fluctuations of airglow emission rate and rotational temperature were of the order of ∼0.07–0.15 and ∼0.02–0.04, respectively, and the characteristic vertical wavelengths were estimated at ∼10 2 -20 km. The inferred r.m.s. horizontal velocities and velocity variances were found to be ∼12–25 m/s and ∼150–600 m²/s², with the majority of the horizontal velocity and its variance associated with low-frequency, large-scale wave motions. The estimated momentum fluxes, mainly contributed by high-frequency, small-scale waves, were ∼2–10 m²/s². These results are in good agreement with those obtained from other measurements using different observational methods at low and mid-latitudes.     

The analysis of hydroxyl rotational temperatures to characterize moving thermal structures near the mesopause

Hydroxyl (OH) rotational temperatures near 85 km altitude have been monitored at Calgary, Alberta, Canada (51°N, 114°W) since 1981 with the objective of determining velocities, wavelengths and periods associated with moving temperature structures. A technique is described whereby the velocity of moving patterns in two dimensional data sets can be accurately determined and used as a parameter for a global smoothing algorithm. Velocities of the structures in the meridional direction were found to be directed poleward. Corresponding Doppler bulk wind velocities measured near the 95 km height region were directed equatorward indicating the presence of filtering of internal gravity waves by the background wind. Two coherent wave structures were often observed simultaneously during a night. The smaller of the two structures had true wavelengths less than 15–30 km and may be related to billow clouds often reported in noctilucent cloud observations. The second wave has a period on the order of an hour and meridional wavelengths ranging from 100 to 2000 km.     

Rotational temperatures for OH and O2 airglow bands measured simultaneously from El Leoncito (31°48′S)

Some results from 54 nights of simultaneous measurements, performed between 1984 and 1987, of rotational temperatures for the OH(6−2) and O₂(¹∑)(0–l) bands are presented. A summer enhancement by 15 K in O₂ temperature has been found that has not formerly been observed in airglow measurements. At least five nights show prominent tide-like temperature oscillations with a phase shift between layers typical of upward wave propagation at about 10 km h⁻¹, with up to 55 K variation. During other nights, similar oscillations are limited to the O₂ layer. Data for different seasons seem to be characterized by different levels of variability. During the one equinox campaign, nocturnal temperature variations show an exceptionally stable pattern of tide-like oscillations.     

Wave characteristics obtained from OH rotational temperatures and 557.7 nm airglow intensities

Variations of OH rotational temperature and 557.7 nm atomic oxygen intensity have been measured from Calgary, Alberta, Canada (51°10′N, 114°13′W) from 1985 to 1987. For three nights studied in detail the OH rotational temperature wave structure at 85 km was negatively correlated with the green line emission at 95 km, indicating that wave activity linked the two regions. The lower altitude region displayed high and low frequency wave structure, but by 95 km the high frequency component had disappeared. Temperature data from 16 nights during which there was obvious wave activity yielded horizontal wavelengths from about 5–100 km and inferred vertical wavelengths from 0.7 to 8 km. The horizontal and vertical angles of propagation imply a statistical source to the observed waves as being located south of Calgary along the Rocky Mountain range. There appeared to be very few, if any, wave structures propagating towards the southeast indicating a probable filtering mechanism by the background winds between the Earth's surface and 85 km.     

On significant quantities of negative ions observed around the mesopause

Significant amounts of negative ions are sometimes observed at altitudes as high as the mesopause region (Kopp E. and Hermann L., 1984, Annales Geophysical2, 83; Ganguly S., 1984, J. atmos. terr. Phys. 46, 633). Using a suitable ion-chemical scheme in which water clustering to negative ions is also considered, the effect of change in temperature, T, and concentrations of NO, O, O₃ and H₂O on the abundance of negative ions in the mesopause region has been examined. It is shown that a drastic increase in the concentration of O₃ or a decrease in neutral temperature by about 20 K. around 85km could make the concentration of total negative ion comparable to that of electron.     

Studies of high latitude mesospheric turbulence by radar and rocket 1: energy deposition and wave structure

During early spring, 1985, the MAE-3 (Middle Atmospheric Electrodynamics) Program was conducted at Poker Flat Research Range, Alaska to study the origin of wintertime mesospheric echoes observed with the Poker Flat MST radar there, by probing the mesosphere with in situ rocket measurements when such echoes occurred. Pre-launch criteria required the appearance of echoes exhibiting some wave structure on the MST radar display; these could be met even under weak precipitation conditions with riometer absorption near or above 1.0 dB. Two morning rockets were launched under such conditions, the first (31.048) on 29 March 1985, at 1703 UT and the second (31.047) on 1 April 1985, at 1657 UT. Both payloads were deployed on a high altitude parachute near a 95 km apogee to provide a stable platform for data acquisition within the mesosphere (below 80 km). Each payload carried a solid state detector to measure energetic electrons between 0.1 and 1.0 MeV and an NaI crystal detector to measure x-rays from >5 to >80 keV. Payload 31.048 also carried a positive ion ‘turbulence’ probe which measured ion density changes (ΔN_i/N_i) during payload descent, whereas 31.047 carried a nose tip ‘turbulence’ probe designed to measure electron density changes (ΔN_e/N_e) during upleg ram conditions plus a Gerdien condenser for the measurement of bulk ion properties during downleg. The energy deposition curves for each event exhibited peak deposition rates between 75 and 80 km with a half width of 16–18 km, almost exclusively induced by precipitating relativistic electrons. They also showed a maximum bottomside gradient between 65 and 75 km. Radar echoes and atmospheric turbulence were observed in the same altitude domain, consistent with the anticipated need for adequate free thermal electron gradients to make such phenomena visible on the radar. The vertical wave structure from radar echoes was found to be consistent with that observed in horizontal wind and temperature profiles measured by Datasondes flown shortly after each large rocket. An analysis of the wave structure from radar data has shown that although large scale waves (λ_z ~ 7 km) were found to be present, a higher frequency shorter wavelength (∼ 1–3 km) component probably played a more significant role in modulating the signal-to-noise structure of the radar echoes.     

Simultaneous optical observations of long-period gravity waves during AIDA '89

Ground-based optical instrumentation supported the AIDA '89 wind measurement comparisons by describing the gravity waves affecting the 80–100 km altitude region during clear dark hours over Puerto Rico. This study tabulates the characteristics of gravity waves with fractional column emission rate amplitudes up to 30% and with periods greater than 45 min as seen in the O₂ airglow layer by MORTI, a sensor of O₂ rotational temperature and column emission rate in twelve look directions. Data from seven other sensors operating at Guanica and the Arecibo Observatory are then compared with the MORTI data to check the consistency of the entire data set with the wave parameters, primarily velocities, deduced from MORTI. Nine nights of visually distinct crests and troughs were found, one of which was dominated by an evanescent wave and the rest by internal waves. The nights of 5/6 April and 4/5 May 1989 were selected for multi-sensor comparisons. The comparisons showed substantial agreement between the MORTI characterizations and the observations by others, and most differences were attributed to complexities introduced by higher frequency components with shorter coherence distances. Nightly summaries of the O₂ rotational temperature and column emission rate are also given.     

Radar and optical observations of mesospheric wave activity during the lunar eclipse of 6 July 1982

Simultaneous measurements were made using a 2.66 MHz interferometer radar, infrared photometers, and imaging systems during the total lunar eclipse of 6 July 1982. The radar data showed that a series of six discrete scatterers passed overhead at 103 km with an average spacing of 54 min, and two passed overhead at 88 km, also 54 min apart. The 88 km events were approximately 27 min out of phase with those at 103 km. One of the 88 km events was examined in detail; the radar returns appeared to come from a single scatterer or a few clustered scatterers, with a velocity of 135 m s⁻¹ almost due south, at 6° below the horizontal. The speed and period give a horizontal wavelength of 440 km, and the phase shift between 88 and 103 km activity suggests a 30 km vertical wavelength, in agreement with values for typical medium-scale traveling ionospheric disturbances (TIDs). Infrared images were made in the near infrared, and photometric measurements were made on and off the 8−3 band of OH. These observations, made from one site near the radar and a second site 575 km south, showed wavelike structures appearing first over the radar, then further south until they filled most of the sky. The speed of development of the infrared structure pattern in the sky is consistent with the 135 m s⁻¹ southward wave speed observed by the radar, but the structures themselves appeared in place, then drifted slowly northward at 10 m s⁻¹. The photographically determined wavelengths were 30–60 km, considerably shorter than the 440 km determined with the radar.     

Thermospheric and mesospheric temperatures during geomagnetic storms at 23°S

Night-time thermospheric temperatures, T63o, and mesospheric rotational temperatures, T(OH) and T(O₂), have been measured at Cachoeira Paulista (23°S, 45°W, 16°S dip latitude), located in both the equatorial ionospheric anomaly and the South Atlantic Geomagnetic Anomaly, with a Fabry-Perot interferometer and a multi-channel tilting filter-type photometer, respectively. The thermospheric temperatures are obtained from the Doppler line broadening of the OI 630.0 nm emission and the mesospheric rotational temperatures from the OH(9,4) and O₂A(0,1) band emissions. Measurements made during three geomagnetic storms showed that the nocturnal mean values of T₆₃₀ during the recovery phase of the storms were lower than those observed during quiet time and from model predictions. Also, the nocturnal mean value of the T₆₃₀ soon after the SSC event on 27 June 1992 was higher than the quiet time and model predictions. The observed mesospheric nocturnal mean rotational temperatures, T(O₂) and T(O₂), were unaffected by the storms. A comparison of the night-time observed temperatures T₆₃₀, T(OH) and T(O₂) with those calculated using the MSIS-86 model is also presented.